Resonant inelastic x-ray scattering from magnetic systems with angular resolution and polarization analysis of the scattered beam: Results on metallic Co, Fe, and Co ferrite at theL3,2edges

Abstract

We present experimental results on resonant inelastic x-ray scattering (RIXS) in perpendicular geometry excited with circularly polarized x rays at the Co ${L}_{3,2}$ edges in Co ferrite $(\mathrm{Co}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})$ and Co metal and at the Fe ${L}_{3,2}$ edges in Fe metal. In this geometry with magnetic samples the incident x-ray beam is perpendicular to the magnetization and the magnetic dichroism is only present in RIXS. We study the $3s$-RIXS channel terminating in an inner shell $3s$ hole and extra $3d$ electron $(2{p}^{6}3{d}^{n}\ensuremath{\rightarrow}2{p}^{5}3{d}^{n+1}\ensuremath{\rightarrow}2{p}^{6}3{s}^{1}3{d}^{n+1})$. The work is based on the measurement of the spectra vs incident photon energy and integrated over the scattered photon energy. We present data resolved in linear polarization of the scattered beam for scattering at 45\ifmmode^\circ\else\textdegree\fi{} and data summed over the outgoing polarizations and taken vs the scattering angle $\ensuremath{\varphi}$. The results show common features in both metals and ionic system: the dichroism scales as $\mathrm{sin}\phantom{\rule{0.2em}{0ex}}2\ensuremath{\varphi}$ while the spectral shape remains constant. The dichroism is maximum when the outgoing linear polarization is in the scattering plane and zero when the outgoing linear polarization is perpendicular to the scattering plane. The presence of the dichroism is due to the breaking of the mirror symmetry of the geometry consisting of the helicity vector of the incident radiation, the sample magnetization, and the linear polarization of the scattered beam. This is expected, in general, when the scattering occurs without rearrangement in the intermediate state. It is noteworthy that this occurs also in the metallic systems, where the scattering takes place with rearrangement due to a spin-dependent screening of the intermediate state core hole. This shows that this rearrangement does not require a more complex vector system in its description. The results show the relation between the selection of the scattering angle and the measurement of the polarization of the scattered radiation. We also present results from a geometry where the dichroism is absent in the emission integrated over outgoing polarization but where it is observed when this polarization is selected.